《过程控制技术》课件-热电偶测温原理

PrincipleofTemperatureMeasurementbyThermocouple热电偶测温原理落版在此谢聪XieCong主讲教师Teacher生产的安全、效率与产品质量Productionsafety,efficiencyandproductquality温度的精准测量如同“定海神针”Accuratetemperaturemeasurementactslikea"pillarofstability,"工业生产Industrialproduction热电偶测温原理PrincipleofTemperatureMeasurementbyThermocouple热电偶Thermocouple测量范围Measurementrange可靠性能Reliability便捷使用Easeofuse“中流砥柱”"Backbone"热电偶测温原理PrincipleofTemperatureMeasurementbyThermocouple高温熔炉High-temperaturefurnace低温冷藏Low-temperaturestorage化工反应釜Chemicalreactor电力锅炉Electricboiler热电偶测温原理PrincipleofTemperatureMeasurementbyThermocouple如何感知温度的变化?Howisthetemperaturechangesensed?为何能在复杂的工业环境中稳定发挥作用？Whycanitfunctionstablyincomplexindustrialenvironments?热电偶测温原理PrincipleofTemperatureMeasurementbyThermocouple热电偶测温Thermocoupletemperaturemeasurement热电偶测温原理PrincipleofTemperatureMeasurementbyThermocoupleCaseimport案例导入在某钢铁厂的炼钢车间，一场紧张的生产正在进行。高温熔炉内，钢水翻滚，温度高达1600℃，而此刻，精准把控温度成为确保钢材质量的关键。工人依靠安装在熔炉内的热电偶，时刻监测着温度变化。Inthesteelmakingworkshopofasteelplant,anintenseproductionisgoingon.Insidethehigh-temperaturefurnace,themoltensteelchurnsattemperaturesreachingupto1,600°C.

Atthismoment,accuratetemperaturecontrolhasbecomethekeytoensuringsteelquality.Workersrelyonthermocouplesinstalledinthefurnacetomonitortemperaturechangesallthetime.Caseimport案例导入但在一次生产过程中，热电偶出现故障，温度反馈延迟，致使炉温失控。原本应保持在合适区间的温度急剧攀升，超出了正常范围。这直接导致炼出的钢材内部结构产生缺陷，大量钢材报废，企业损失惨重。However,inaproductionprocess,thethermocouplefailedandthetemperaturefeedbackwasdelayed,resultinginthefurnacetemperaturegettingoutofcontrol.Thetemperaturethatshouldhavebeenkeptintherightrosesharply,beyondthenormalrange.Thisdirectlyledtodefectsintheinternalstructureoftherefinedsteel,alargeamountofsteelwasscrapped,andtheenterprisesufferedheavylosses,PrincipleofTemperatureMeasurementbyThermocouple热电偶测温原理PrincipleofTemperatureMeasurementbyThermocouple热电偶测温原理热电偶是基于热电效应的测温元件，能将温度信号转换成毫伏（mV）级电势信号。一般用于测量500～1600℃之间的温度。Thermocoupleisatemperaturemeasuringelementbasedonthethermoelectriceffect,whichcanconvertthetemperaturesignalintoamillivolt(mV)potentialsignal.Itisgenerallyusedtomeasuretemperaturesbetween500and1,600°C.热电偶Thermocouple两种不同材料的导体或半导体材料A和B连接成闭合回路时，若两个接点温度不同，回路中会产生热电势，热电势由接触电势和温差电势两部分组成。IfthetemperaturesofthetwocontactsaredifferentwhentwoconductorsorsemiconductormaterialsAandBofdifferentmaterialsareconnectedtoformaclosedloop,athermoelectricpotentialwillbegeneratedintheloop.Thethermoelectricpotentialconsistsoftwoparts:contactpotentialandtemperaturedifferencepotential.热电偶测温原理PrincipleoftemperaturemeasurementbythermocouplePrincipleofTemperatureMeasurementbyThermocouple热电偶测温原理接触电势Contactpotential当两种不同材料的导体A

和B

接触时，由于材料内部电子密度不同，会发生电子扩散，在接触界面形成电场，产生接触电势，且温度t

高于t₀时，会进一步影响电子扩散和电势大小。WhenconductorsAandBoftwodifferentmaterialsareincontact,electrondiffusionwilloccurduetothedifferentelectrondensitiesinsidethematerials,forminganelectricfieldatthecontactinterfaceandgeneratingcontactpotential.Whenthetemperaturetishigherthant₀,itwillfurtheraffectelectrondiffusionandpotentialmagnitude.温差电势Temperaturedifferencepotential对于单一导体，当两端温度不同（t≠t₀）时，高温端的电子能量高于低温端，电子会从高温端向低温端扩散，从而在导体两端形成电势差，即温差电势。Forasingleconductor,whenthetemperaturesatbothendsaredifferent(t≠t₀),theenergyofelectronsatthehigh-temperatureendishigherthanthatatthelow-temperatureend,andelectronswilldiffusefromthehigh-temperatureendtothelow-temperatureend,thusformingapotentialdifferenceatbothendsoftheconductor,thatis,temperaturedifferencepotential.PrincipleofTemperatureMeasurementbyThermocouple热电偶测温原理对于材质确定的热电偶，热电势仅与热端和冷端温度有关，当冷端温度固定时，热电势E(t,t₀)是热端温度t的单值函数。Forthermocoupleswithdeterminedmaterial,thethermoelectricpotentialisonlyrelatedtothetemperatureofthehotendandthecoldend.Whenthecoldendtemperatureisfixed,thermoelectricpotentialE(t,t₀)isamonodromefunctionofthehotendtemperaturet.通过实测得到热端不同温度t

时的热电偶电势，制成热电偶分度表，方便实际应用中查阅使用。Thethermocouplepotentialofthehotendatdifferenttemperaturestcanbeobtainedbyactualmeasurement,andathermocouplegraduationtablecanbemade,whichisconvenientforreferenceanduseinpracticalapplication.在冷端温度t₀=0℃的条件下Theconditionthatthecoldendtemperaturet₀=0°CThermocouplegraduationtable热电偶的分度表Thermocouplegraduationtable热电偶的分度表t/℃0010203040506070809000.0000.3970.7981.2031.6112.0222.4362.8503.2663.6811004.0954.5084.9195.3275.7336.1376.5396.9397.3387.7372008.1378.5378.9389.3419.74510.15110.56010.96911.38111.79330012.20712.63213.03913.45613.87414.29214.71215.13215.55215.97440016.39516.81817.24117.66418.08818.51318.93819.36319.78820.21450020.64021.06621.49321.91922.34622.77223.19823.62424.05024.47660024.90225.32725.75126.17626.59927.02227.44527.86728.28828.70970029.12829.54729.96530.38330.79931.21431.62932.04232.45532.86680033.27733.68634.09534.50234.90935.31435.71836.12136.52436.92590037.32537.72438.12238.51938.91539.31039.70340.09640.48840.897100041.26941.65742.04542.43242.81743.20243.58543.96844.34944.729110045.10845.48645.86346.23846.61246.98547.35647.72648.05948.462120048.82849.19249.55549.91650.27650.63350.99051.34451.69752.049130052.398镍铬—镍硅热电偶分度表（简表）GraduationTableofNickel-Chromium-Nickel-SiliconThermocouples(AbridgedTable)分度号为KThegraduationnumberisK冷端温度t₀=0℃Thecoldendtemperaturet₀=0℃确定热端温度t：假设热端温度为t=250℃。Determinethehotendtemperaturet:Assumethatthehotendtemperatureist=250°C.查找行和列：在表格的第一列（t/℃）中找到最小于并接近250℃的行，即200℃。Findtherowandcolumn:Locatetherowinthefirstcolumn(t/℃)thatisthelargestvaluelessthanorequalto250°C,whichis200°C.确定热电势E：在200℃行和50

列的交叉处，找到对应的数值为10.151mV。DeterminethethermoelectricpotentialE:Attheintersectionofthe200°Crowandthe50column,thecorrespondingvalueis10.151mV.Thermocouplegraduationtable热电偶的分度表热电偶两个接点温度为t

和t₀时，回路产生的热电势等于接点温度为t、t₁和t₁、t₀时，两支同性质热电偶产生的热电势代数和。Thetemperaturesofthetwocontactsofthethermocouplearetandt₀.Atthistime,thethermoelectricpotentialgeneratedbytheloopisequaltothealgebraicsumofthethermoelectricpotentialsgeneratedbythetwothermocouplesofthesamenaturewhenthecontacttemperaturesaret,t₁andt₁,t₀,中间温度定律IntermediatetemperaturelawEAB(t,t0)=EAB(t,

t1)+EAB(t1,t0)Thermocouplegraduationtable热电偶的分度表t/℃0010203040506070809000.0000.3970.7981.2031.6112.0222.4362.8503.2663.6811004.0954.5084.9195.3275.7336.1376.5396.9397.3387.7372008.1378.5378.9389.3419.74510.15110.56010.96911.38111.79330012.20712.63213.03913.45613.87414.29214.71215.13215.55215.97440016.39516.81817.24117.66418.08818.51318.93819.36319.78820.21450020.64021.06621.49321.91922.34622.77223.19823.62424.05024.47660024.90225.32725.75126.17626.59927.02227.44527.86728.28828.70970029.12829.54729.96530.38330.79931.21431.62932.04232.45532.86680033.27733.68634.09534.50234.90935.31435.71836.12136.52436.92590037.32537.72438.12238.51938.91539.31039.70340.09640.48840.897100041.26941.65742.04542.43242.81743.20243.58543.96844.34944.729110045.10845.48645.86346.23846.61246.98547.35647.72648.05948.462120048.82849.19249.55549.91650.27650.63350.99051.34451.69752.049130052.398可利用冷端为0℃时的热电势关系（查分度表），求出冷端为任意温度时的热电势。Youcanusethethermoelectricpotentialrelationshipwhenthecoldendis0°C(checkthegraduationtable)tocalculatethethermoelectricpotentialwhenthecoldendisatanytemperature.EAB(t,t0)＝EAB(t,0)-EAB(t0,0)=符合分度表要求

Conformtograduation

tablerequirements

ABt0t

AB0t

AB0t0

---Thermocouplegraduationtable热电偶的分度表练习：假如用K型热电偶测量某加热炉温度。测得热电势为E(t,t0)=36.122mV，而冷端温度t0=30℃，求被测点的实际温度。Exercise:SupposeaK-typethermocoupleisusedtomeasurethetemperatureofaheatingfurnace.ThemeasuredthermoelectricpotentialisE(t,t0)=36.122mV,andthecoldendtemperaturet0

=30℃.Findtheactualtemperatureofthemeasuredpoint.t/℃0010203040506070809000.0000.3970.7981.2031.6112.0222.4362.8503.2663.6811004.0954.5084.9195.3275.7336.1376.5396.9397.3387.7372008.1378.5378.9389.3419.74510.15110.56010.96911.38111.79330012.20712.63213.03913.45613.87414.29214.71215.13215.55215.97440016.39516.81817.24117.66418.08818.51318.93819.36319.78820.21450020.64021.06621.49321.91922.34622.77223.19823.62424.05024.47660024.90225.32725.75126.17626.59927.02227.44527.86728.28828.70970029.12829.54729.96530.38330.79931.21431.62932.04232.45532.86680033.27733.68634.09534.50234.90935.31435.71836.12136.52436.92590037.32537.72438.12238.51938.91539.31039.70340.09640.48840.897100041.26941.65742.04542.43242.81743.20243.58543.96844.34944.729110045.10845.48645.86346.23846.61246.98547.35647.72648.05948.462120048.82849.19249.55549.91650.27650.63350.99051.34451.69752.049130052.398从分度表查得K

型热电偶E(30,0)=1.203mV。Fromthegraduationtable,findK-typethermocoupleE(30,0)=1.203mV.查阅分度表，确定被测点温度为900℃。Consultthegraduationtableagaintodeterminethatthemeasuredpointtemperatureis900°C.则

E(t,0)=E(t,30)+E(30,0)=36.122+1.203=37.325mV

Then

E(t,0)=

E(t,30)+E(30,0)=36.122+1.203=37.325mV

PrincipleofTemperatureMeasurementbyThermocouple热电偶测温原理温度信号Temperaturesignals热电偶Thermocouples热电势信号Thermoelectricpotentialsignals热电效应Thermoelectriceffect再通过与分度表结合以及中间温度定律等，实现对温度的准确测量，在工业生产、科学研究等众多领域有着广泛且重要的应用。Throughcombinationwithgraduationtablesandlawsliketheintermediatetemperaturelaw,theyachieveaccuratetemperaturemeasurementandarewidelyandcriticallyappliedinindustrialproduction,scientificresearch,andmanyotherfields.PrincipleofTemperatureMeasurementbyThermocouple热电偶测温原理关乎生产安全Crucialforproductionsafety国之重器质量QualityofthecriticalnationalinfrastructurePrincipleofTemperatureMeasurementbyThermocouple热电偶测温原理锤炼灵敏可靠的专业本领；Honekeenandreliableprofessionalskills;以毫伏级的精准担当，守护中国制造的生命线。To